Whiles and Fors (Notes 3)

While Loop

A while loop is a way to run some amount of code while some condition exists.

Everything within the while loop should be tabbed over by 1 tab, unless it is within an if statement, another loop, or within some other statements.

It uses conditions with the same operators as the If Statement notes.

    #This example shows a while loop in use
    while(lunchBreak==True):
        print("eating lunch")

Be Careful with the Condition

If a while loop condition is always true, it will end up causing an infinite loop which breaks your program, so make sure you are careful with what while loop condition you choose.

For Loop

A for loop is similar to a while loop, but you get to define how many iterations (the amount of times the loop runs) the for loop has.

It is typically good to use in arrays/lists or certain pieces of code where you would want to do certain things for specific amounts of time. Everything inside of a for loop should be tabbed like a while loop.

There are different ways of writting a for loop. One of the ways is shown below:

    #This example shows a for loop
    for i in range(0,5):
        print("Hello")

tip

The above code will run 5 times. The 'i' is just an integer saying which iteration (which loop count the for loop is on). The loop starts at 0 and ends at 4, and that is what range(start,end) does. In our case, the start is 0, and the end is 5.

Be Careful with the Range

In a range, the last number is always cut-off, so the loop does not go for 6 times, but only for 5 times, and the 0 counts as the first iteration.

Another example below shows how we can utilize the 'i', which can be any variable name, inside of a for loop.

    #This is another for loop
    for i in range(0,6):
        print("Hi " + str(i))

The last thing the output would print is "Hi 5", and in this way, the 'i' can also be used within the for loop.

There are other ways a for loop can be done, such as using a list, but it will not be discussed in this notes page.